This “hands free” access system is known to those skilled in the art. It is generally composed of an electronic control unit on board the vehicle, of one or more radio frequency (RF) antenna(s) situated on the vehicle and of a tag or a remote control for identification purposes, comprising an RF antenna carried by the user.
An exchange of Identifying Data (ID) between the tag and the vehicle by way of the RF antennas allows the identification of the tag by the vehicle and the triggering of the locking or unlocking of the opening panels by the latter.
The ID can be contained in a mobile device other than a tag or a remote control, for example it can be contained in a mobile phone, carried by the user. More and more mobile phones are equipped with NFC (“Near Field Communication”) technology, i.e. technology for communicating in the near field. To do this, they are equipped with an NFC antenna at 13.56 MHz. This near field communication makes it possible to exchange data over radio frequency waves at a short distance, i.e. a distance varying from 0 cm (i.e. the two mutually communicating objects are in contact) up to 10 cm. This type of communication is used to pay a toll, to pay for a parking place, etc, via the user's mobile phone. It can also be used in order to access a vehicle.
In the latter case, “hands free” access systems compatible with near field communication of NFC type comprise an NFC communication antenna at 13.56 MHz on the vehicle, generally incorporated into the driver's door. This antenna will be known as the first primary NFC antenna. The user can thus trigger the locking or unlocking of his vehicle by presenting his mobile phone, which also comprises an NFC antenna (which will be known as the secondary NFC antenna) in front of the primary NFC antenna of the vehicle. The use of the mobile phone instead of a tag opens up possibilities for functions and/or applications that the tag or the remote control cannot offer. This is due to the fact that the mobile phone itself comprises far more applications and functionalities than a simple “hands free” tag for accessing a vehicle. These functions and/or applications comprise the reading of audio files, the storage and transfer of telephone address books or any other data toward a compatible device by wireless communication of NFC type, etc.
For example, once the mobile phone has been identified by the vehicle, it transmits a user profile to the vehicle by NFC communication. This user profile is then used by the vehicle (more precisely by the electronic system on board the vehicle) to personalize the vehicle according to this user profile. It is thus possible to pre-adjust vehicle seats, or radio stations, or else to turn on the air conditioning etc. before the user enters his car, for example.
Some vehicles also comprise incorporated into the passenger compartment, for example on their dashboard, a mobile phone charging appliance, such as a mobile phone charger, that is compatible with NFC communication. That is to say, this charging device makes it possible, not only to electrically charge the mobile appliance, but also to exchange data by NFC communication between this appliance and the on-board system of the vehicle. To do so, this charging device further incorporates another NFC antenna, which will be called second primary NFC antenna. When the telephone is placed on the charger, in order to be recharged with electricity over a wired link or by induction, an NFC communication is triggered between the second primary NFC antenna of the vehicle and the secondary NFC antenna of the mobile phone. A transfer of data from the mobile phone toward the vehicle is then carried out. This data transfer can consist in a download of audio files of .mp3 (“Moving Picture Experts Group Audio layer 3”) format, contained in the telephone that the user wishes to listen to over the hi-fi system of his vehicle. It can also consist in a download of the address book of the mobile phone so that this same address book can be consulted by the user on a screen of the vehicle (screen shared by the radio, and/or the navigation system of the vehicle).
Of course, when the mobile phone is placed on the charger, i.e. when it is found in immediate proximity or even in contact with the second primary NFC antenna, over a relatively long time period, a continuous download of files to the on-board vehicle system can be carried out. Long downloads, or downloads of files of large size are not possible when the telephone is presented only for a very short time period in front of the first primary NFC antenna dedicated to accessing the vehicle.
Since NFC communication takes place at short distances (in the order of a few centimeters), it is more secure than an RF communication that is performed a few meters away around the vehicle. This is why more and more hands free vehicle access tags offer, like mobile phones, the option of communication with the vehicle by NFC in addition to remote access via RF. In an example of use, the tag is detected far off, and its ID recognized by the vehicle by way of RF communication, then the unlocking of the opening panels of the vehicle is performed only when the user presents his tag at a few centimeters from the door, i.e. when the tag communicates with the vehicle by NFC. Access to the vehicle is then secured by the presence of the tag in immediate proximity to the vehicle, which limits the risks of break-ins.
A primary NFC antenna on board a vehicle is configured initially in an optimal manner to communicate with a single type of mobile device, i.e. either with a tag or with a mobile phone, and the latter as a function, furthermore, of the size of the secondary NFC antenna situated in this same mobile device.
Indeed, to ensure a communication of optimal quality, the size and the impedance of the primary NFC antenna must be configured differently, according to whether the primary NFC antenna communicates with a tag (whose secondary NFC antenna size is relatively small but whose impedance and therefore communication range is relatively large) or with a mobile phone (whose secondary NFC antenna is generally larger than that of a tag, but whose impedance and therefore communication range are relatively small.) The size of the primary NFC antenna, on board the vehicle, must be calibrated as a function of the size of the secondary NFC antenna situated in the mobile device and its impedance must be calibrated as a function of a typical distance or of an average distance of communication between the two. Ideally, both the primary and secondary NFC antennas of the vehicle and of the mobile device must be of substantially equal size to ensure good quality communication between them.
The configuration of the primary NFC antenna is important because, for example, a primary NFC antenna whose impedance is too high with respect to a given communication distance from the secondary NFC antenna creates problems of de-adaptation of the secondary NFC antenna of the mobile device and problems of communication between the two. Conversely, an excessively low impedance reduces the range of the primary NFC antenna and problems of detection of the mobile device by the vehicle. As to the size of the primary NFC antenna, if it is too small, it emits a very intense and localized electromagnetic field. And a larger secondary NFC antenna situated in the mobile device will have difficulty detecting this localized and intense field.
The configuration (the adjustment of the size and impedance) of the primary NFC antenna can be performed by way of the on-board electronic system of the vehicle using an electronic circuit comprising selectors and/or switches. These selectors and/or switch(es) make it possible to adapt the size of the antenna by linking or not linking several parts of the primary antenna with each other. They also make it possible to adjust the impedance by selecting for each part of the antenna a precise number of windings of the copper wire. These devices and methods of antenna configuration are the subject of another patent application, filed by the Applicant on the same day as the present application.
It will be understood that, due to the applications and/or functionalities and the antenna configuration, which differ according to whether the mobile device is a mobile phone or a tag (or any other device), it is necessary for the vehicle to be able to distinguish these mobile devices apart from each other and therefore to be able to characterize the type of the mobile device. This is necessary, not only in order to establish good quality NFC communication as fast as possible by configuring the antenna in a appropriate way, but also to avoid trying to establish impossible communications. Indeed, if the telephone/tag distinction is not made, the vehicle can pointlessly try to send vehicle data to the tag (as it does for a mobile phone) that the tag is not able to process as the mobile phone does. Specifically, the mobile phone can trigger applications on the basis of these data, whereas the tag, as explained previously, does not offer this possibility.
Moreover, it is also necessary to detect the approach mode of the mobile device toward the vehicle, i.e. to discern whether the mobile device is in dynamic approach, i.e. if it is approaching the vehicle, which is the case during access to the vehicle, or if it is in static approach, i.e. situated at a fixed distance with respect to the primary NFC antenna. Indeed, in the case where the mobile device is a mobile phone and it is at a fixed distance from the vehicle, the on-board system of the vehicle can trigger applications specific to the configuration of the vehicle or to the access to the vehicle, which is not possible with a tag (whether it is situated at a fixed distance or is approaching the vehicle), and which is also not possible when the mobile phone is quickly approaching the vehicle.
Moreover, the content of the communication between the mobile device and the vehicle differs according to whether the mobile device is at a fixed distance from the primary antenna dedicated to the vehicle access or is situated at a fixed distance from the secondary antenna situated on the charging device. In the latter case, if the mobile device is a mobile phone, then files of larger size and continuous downloads can be envisioned. Specific applications dedicated to the interaction with the navigation system or with the audio system of the vehicle can be launched. On the other hand, if the mobile device is a tag, this discernment with regard to the approach mode (static or dynamic) has no use, because no download can be performed with a tag.